1. Field of the Invention
This invention relates generally to containers housing a pressurized medium and includes self-chilling or self-heating food and beverage containers, aerosol containers or the like. More specifically, this invention is directed to a valve incorporated into such containers which will automatically relieve pressure built up in the container upon such pressure reaching a predetermined level and at the same time can function to provide the normal desired operation of the container.
2. Description of Prior Art
The prior art directed to aerosol valves and to self-chilling and self-heating food and beverage containers is quite extensive. A major problem with regard to containers particularly in these arts which house a pressurized medium utilized in dispensing the contents of the container or to heat or chill the contents of the container is that the pressure of the medium can, under certain circumstances, reach a level, if not controlled, which will cause a container to rupture and possibly even explode thereby imparting injury to users. Various attempts have been made with such prior art containers to relieve the pressure prior to serious rupture of the container or the explosion of the container. One over pressure relief mechanism used particularly in aerosol cans, includes having the necked in portion of the can stretch to increase the volume. This will cause the valve cup which carries the dispensing valve to also move. If the over pressurized condition within the container increases sufficiently, it causes the valve cup to move by an amount sufficient that causes the periphery thereof to release from the edge of the container thereby allowing the over pressure condition to be relieved and in some instances the valve will fly off from the container and can potentially injure someone.
Another feature which has been embodied in such containers is to coin a portion of the bottom of the container to weaken a section thereof in such a manner that when the pressure internally of the container reaches a predetermined level, the material forming the container around the coined area releases and the contents of the pressurized medium exit the container, thereby relieving the over pressure condition.
feature which has been utilized under certain circumstances is to permit the concave bottom of the can to expand outwardly thus increasing the volume in the can.
An additional over pressure mechanism which has been embodied in containers, particularly those directed to self-chilling or self-heating food and beverage containers is illustrated in U.S. Pat. No. 6,732,886 which is incorporated herein. This patent discloses an over pressure release mechanism which includes a valve member having a valve stem for releasing the pressurized medium upon activation. The valve member is carried by a pedestal which is moveable relative to the container upon pressure in the container reaching a predetermined level. A barrier is disposed adjacent the valve stem and is anchored to the container. When the pedestal moves by a predetermined amount responsive to pressure reaching the predetermined level, the valve stem engages the barrier activating the valve which relieves the over pressure condition. This apparatus has been proven to be effective for the purpose intended.
The over pressure mechanism, as shown in U.S. Pat. No. 6,732,886 is illustrated in FIG. 1. As therein shown a container 12 housing a beverage 14 has a top 16 formed in the usual manner and could include a lift tab (not shown) as is well known in the prior art. A heat exchange unit 20 having a valve 18 secured to a pedestal 22 is secured to the top portion 24 of the HEU 20 by crimping as is well known in the prior art. The valve 18 includes a valve stem 26. Upon activation of the valve stem 26, a pressurized gas such as carbon dioxide may be directed internally of the HEU 20 through an orifice 28 in the valve to be adsorbed by a carbon plug 38 comprised of compressed activated charcoal or the like and may include a binder and other materials. A cap 30 is disposed over the valve stem 26 to protect it from inadvertent activation. Internally of the cap 30 there is provided a barrier 32 disposed adjacent the top of the valve stem 26. When the pressure internally of the HEU 20 increases beyond a predetermined amount, the pedestal 22 moves toward the bottom of the container 12, and as such occurs, the valve stem 26 contacts the barrier 32 and causes the stem to become activated thereby releasing the pressure built up internally of the HEU.
Even though this apparatus as shown in FIG. 1 functions very well for the purpose intended, a need exists for an over pressure mechanism housed internally of the valve and constructed in such a manner that the valve will normally operate but at the same time will be activated by an over pressure condition to release the over pressure internally of the HEU without causing the pedestal of the HEU to expand or move as has been the case in the prior art.